Effect of diet supplementation on production and reproduction of crossbred heifers

An experiment was carried out to study the effects of levels of concentrate supplementation on body weight, subsequent milk production and reproductive traits of 50% and 75% exotic crossbred heifers. Forty-six heifers at six months of age stratified by blood level and body weight were allocated to four supplement treatment groups. The treatments were 250, 500, and 100 g per 100 kg body weight and 500 g/head/day. A supplement was fed on group base until heifers showed first estrus. All heifers were allowed to graze natural pasture for seen to eight hrs per day and in addition had free access to hay at night. The effects of level of supplementation and exotic blood level were not apparent on heifers live weight up to 450 days of age. While, concentrate level significantly (p0.05) affected weights at 540 and 630 days of age. Mean body weight at first heat, conception and calving were 268, 281 and 284 kg, respectively. The effect of level of supplementation and exotic blood level on weight at different repoductive stages was not apparent (p0.05). Heifers fed 1000 g concentrate /100 kg body weight reached age at first heat, conception and calving 245, 359 and 360 days earlier than those fed 500 g/head/day, respectively (p0.05). Half-bred heifers had first heat, conception and calving 50, 46 and 44 days earlier than 75% exotic crosses, respectively. Daily milk yield, 305-days milk and daily body weight gain of heifers fed 1000 g/100 kg body weight were 0.50 kg, 206 kg and 0.1 kg greater than those fed 500 g concentrate/day (p0.05). From the results of this study it could be suggested that supplementation of 1000 g concentrate per 100 kg body weight enables crossbred growing heifers to achieve rapid growth and increased milk production. Heifers could start the reproductive cycle at 270 kg body weight and the time needed to rach this weight could be reduced by almost one year and this may consequently increase the overall life time productivity of the animals.